This invention relates to the guide lugs of reinforced elastomeric endless traction bands, which are used on heavy vehicles like defence vehicles. More specifically, the invention relates to guide lugs to minimize de-tracking occurrences.
The guidance of elastomeric traction bands is generally carried out with the help of protuberances, called guide lugs, which are periodically disposed on the interior surface of the traction band. In many cases, the guide lugs are lodged in the space defined in between a pair of split wheels. These wheels usually include the road wheels on which the vehicle rests, a sprocket wheel which ensures power transmission from the engine to the traction band and a tension wheel.
By engaging in those spaces, the guide lugs restrain the relative lateral movement of the traction band with respect to the wheels and keep the traction band in its normal operating position. For instance, see U.S. Pat. No. 5,540,489 (Muramatsu et al.), U.S. Pat. No. 5,447,365 (Muramatsu et al.), U.S. Pat. No. 5,320,585 (Kato) and U.S. Pat. No. 5,190,363 (Brittain).
To this day, the design of the guide lugs for endless elastomeric traction bands were based on guide lugs designs used in metallic traction bands. However, since an elastomeric material deforms more than steel, the guide lugs made with elastomeric materials have more tendency to deform and therefore increase the risk of de-tracking occurrences of the traction band. The studies we have conducted have shown that the de-tracking phenomenon is usually the result of an interference between the guide lugs as designed in the prior art and the road wheels. Essentially, the lateral deformation of the guide lugs allows the road wheels to xe2x80x9cclimbxe2x80x9d from one side of the guide lug to the other side.
In order to remedy to this situation, the designers have generated different solutions. First, they have tried to rigidify the guide lugs by choosing more rigid elastomers and by reinforcing them With different types of fabric or structures. The designer also tried to increase the size of the guide lugs.
Secondly, the designers tried to limit the road wheel""s tendency to climb on the guide lugs by lowering the friction coefficient between the wheel and the band, by developing specific elastomeric materials with low friction coefficient or by covering the guide lugs with a more slippery material (Teflon, UHMW-PE, etc.).
Those multiples attempts to diminish the de-tracking phenomenon have diminished these occurrences, but de-tracking remains a major problem for elastomeric traction bands when installed on heavy and fast vehicles like defence vehicles.
The main problem comes from the fact that it is impossible to significantly increase the size of the guide lugs. The lateral dimension (the width) of each guide lug is limited by the available space between the pair of split wheels. This spacing is unchangeable once the vehicle has been designed. The longitudinal dimension (the length) of the guide lugs is also limited by the fact that the traction band follows a circular path around the sprocket wheel and the tension wheel, which brings consecutive guide lugs closer to one another. The length of the guide lugs is therefore limited by the need to avoid contact or interference between two consecutive guide lugs in those areas.
The object of this invention is to define a new guide lug which significantly reduces de-tracking occurrences for a heavy vehicle.
This invention proposes nestable guide lugs which allow consecutive guide lugs to be brought closer to one another.
The nestable guide lugs also have a structure which allow a partial insertion of a guide lug portion into a portion of its neighboring guide lug around the curved portion of the traction band.
The nestable guide lugs permit:
1. To significantly reduce the lateral deformations of the guide lugs by maximizing the length of the guide lugs.
2. To significantly reduce the interference risk with the road wheels by generating an almost continuous wall which prevents the road wheels to climb or get in between two consecutive guide lugs.
3. To favor the reestablishment of the guidance when, in rare occasions, the guide lugs sufficiently deform and start interfering with the road wheels.
There is therefore provided a traction band made from an elastomeric material for a vehicle having a plurality of wheels, said band being adapted to be mounted on said wheels, and comprising a longitudinal axis, an external surface for cooperation with a ground surface and an inner surface, said inner surface comprising a series of guide lugs for cooperation with said wheels, each said guide lug having a front portion and a rear portion with respect to said longitudinal axis, said front portion and said rear portion of adjacent guide lugs being adapted to nest within each other when the traction band travels around some of said wheels.
Other aspects and many of the attendant advantages will be more readily appreciated as the same becomes better understood by reference to the following detailed description and considered in connection with the accompanying drawings in which like reference symbols designate like elements throughout the figures.
The features of the present invention which are believed to be novel are set forth with particularity in the appended claims.